Nitride semiconductor light-emitting device, and method for manufacturing same

ABSTRACT

A nitride semiconductor light-emitting device and a method for manufacturing same for improving the electrostatic discharge (ESD) characteristics of the nitride semiconductor light-emitting device. The light-emitting device includes an active layer formed flat using a low conductivity material, on a first conductive semiconductor layer having a v-pit structure on the upper surface thereof, and a second conductive semiconductor layer, or has a v-pit structure on a junction surface between a second conductive semiconductor layer and an active layer formed flat using a low conductivity material on a first conductive semiconductor layer having a v-pit structure on the upper surface thereof. Thus, a v-pit area has a thickness equal to or greater than a critical thickness and thus has very low conductivity, thereby preventing the flow of a current.

TECHNICAL FIELD

The present invention relates to a nitride semiconductor light-emittingdevice, and a method for manufacturing the same. More particularly, thepresent invention relates to a nitride semiconductor light-emittingdevice, and a method for manufacturing the same, which is configured toimprove electrostatic discharge (ESD) characteristics of nitridesemiconductor light-emitting devices.

BACKGROUND ART

Current leakage relates to characteristic deterioration in reliability,service life, and high-voltage operation of a device, thus it isimportant to manufacture a reliable device based on group III nitridelight-emitting diodes.

It has been known that a group III nitride light-emitting device has badelectrostatic characteristics in comparison with light-emitting devicesmade of other compounds. Since crystal defects occurred on the group IIInitride semiconductor layer grown on a substrate due to a latticemismatch between the substrate and the group III nitride semiconductorlayer, spread of a growth direction of the group III nitridesemiconductor layer occurred, thereby forming a threading dislocation.

The crystal defects increase current leakage of device, and in the caseof introducing an external static electricity, an active layer of thelight-emitting device having many of crystal defects is broken by astrong field. Generally, it is known that crystal defects (threadingdislocation) of 10⁹ to 10¹¹/cm² exist on a GaN thin film.

The electrostatic destruction characteristics of the light-emittingdevice are very important issues related to an application range ofGaN-based light-emitting devices. Particularly, a design of device forwithstanding static electricity generated from package devices andworkers of the light-emitting device is very important parameter forimproving the yield of a final device.

Particularly, electrostatic characteristics have become more importantsince the GaN-based light-emitting device is recently applied to andused in bad condition environments such as outdoor signboards, vehiclelights, etc.

Generally, an ESD of a conventional GaN light-emitting device withstandsseveral thousand volts in a forward direction under Human Body Mode(HBM), whereas it does not withstand several hundred volts in a reversedirection. As described above, the main reason is the crystal defects ofthe device, and also, an electrode design of the device is veryimportant. In particular, since a sapphire substrate is generally usedin GaN light-emitting device as an insulator, the ESD characteristicsare further deteriorated by intensifying a concentration phenomenon ofcurrents around an N-electrode during a practical device operation asthe N-electrode and a P-electrode are formed at the same plane on thestructure of the device.

Various methods configured to improve characteristics of light-emittingdevice and other electronic devices by reducing density of threadingdislocation defect are proposed in the related art as follows.

For instance, in Korean Patent No. 10-1164026 (registration date: Jul.18, 2012), Korean Patent Application Publication No. 10-2013-0061981(publication date: Jun. 12, 2013), and Korean Patent ApplicationPublication No. 10-2014-0145368 (publication date: Dec. 23, 2014) agrowth method was introduced, wherein a Hexagonal v-pit (V-shaped pit)was formed on each of threading dislocations, and when v-pits wereformed on an active layer, the active layer was formed thinly on asidewall and had high band gap so that a barrier height was increasedand non-radiative recombination was minimized, therefore, an internalquantum efficiency is increased. However, the conventional techniqueshave a problem with reduced optical output due to a decrease in anoverall light-emitting region, since the v-pit area of the active layerwas excluded from a light-emitting region in such a structure.

DOCUMENTS OF RELATED ART Patent Documents

(Patent Document 1) Korean Patent No. 10-1164026 (registration date:Jul. 18, 2012)

(Patent Document 2) Korean Patent Application Publication No.10-2013-0061981 (publication date: Jun. 12, 2013)

(Patent Document 3) Korean Patent Application Publication No.10-2014-0145368 (publication date: Dec. 23, 2014)

Non-Patent Documents

“Suppression of Nonradiative Recombination by V-Shaped Pits in GaInN/GaNQuantum Wells Produces a Large Increase in the Light EmissionEfficiency”; A. Hangleiter, F. Hitzel, C. Netzel, D. Fuhrmann, U.Rossow, G. Ade, and P. Hinze; PRL 95, 127402 (2005).

“Origin of forward leakage current in GaN-based light-emitting devices”;S. W. Lee, D. C. Oh, H. Goto, H. J. Lee, T. Hanada, M. W. Cho, and T.Yao; APPLIED PHYSICS LETTERS 89,132117 (2006).

“Improvement of Light Extraction Efficiency and Reduction of LeakageCurrent in GaN-Based LED via V-Pit Formation”; Kayo Koike, Seogwoo Lee,Sung Ryong Cho, Jinsub Park, Hyojong Lee, Jun-Seok Ha, Soon-Ku Hong,Hyun-Yong Lee, Meoung-Whan Cho, and Takafumi Yao; IEEE PHOTONICSTECHNOLOGY LETTERS, VOL. 24, NO. 6, MARCH 15, (2012).

DISCLOSURE Technical Problem

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the related art, and an object of thepresent invention is to provide a nitride semiconductor light-emittingdevice, and a method for manufacturing the same capable of minimizingdegradation of overall uniform luminosity when applying a v-pitstructure to improve the reverse voltage characteristics.

Technical Solution

In order to accomplish the above object, a nitride semiconductorlight-emitting device of the present invention includes: a substrate; afirst conductive semiconductor layer formed on the substrate; ahigh-resistance semiconductor layer formed on the first conductivesemiconductor layer; an active layer formed on the high-resistancesemiconductor layer; and a second conductive semiconductor layer formedon the active layer, wherein the nitride semiconductor light-emittingdevice has a V-shaped (v-pit) structure at a junction surface betweenthe high-resistance semiconductor layer and the first conductivesemiconductor layer, and has a plane or a gradual curved plane structureat a junction surface between the high-resistance semiconductor layerand the active layer.

Desirably, the junction surface between the high-resistancesemiconductor layer and the active layer is a flat surface with no v-pitstructure.

Desirably, the active layer has a plane structure at a junction surfacebetween the active layer and the second conductive semiconductor layer.

Next, a nitride semiconductor light-emitting device according to anotherembodiment of the present invention includes: a substrate; a firstconductive semiconductor layer formed on the substrate; ahigh-resistance semiconductor layer formed on the first conductivesemiconductor layer; an active layer formed on the high-resistancesemiconductor layer; and a second conductive semiconductor layer formedon the active layer, wherein the nitride semiconductor light-emittingdevice has a V-shaped (v-pit) structure on each of junction surfacesbetween the high-resistance semiconductor layer and the first conductivesemiconductor layer, and between the active layer and the secondconductive semiconductor layer, and has a flat surface with no v-pitstructure at a junction surface between the high-resistancesemiconductor layer and the active layer. Desirably, the junctionsurface between the high-resistance semiconductor layer and the activelayer has a plane or a gradual curved plane structure with no v-pitstructure, or the second conductive semiconductor layer has v-pitstructure.

Desirably, the high-resistance semiconductor layer has a siliconimpurity concentration of 10¹⁸/cm³ or less, a magnesium impurityconcentration of equal to or greater than 10¹⁸/cm³, and a thickness of10 nm to 1000 nm.

A method for manufacturing a nitride semiconductor light-emitting deviceincludes: a first step of growing a first conductive semiconductor layeron a substrate while forming a v-pit structure on an upper surface ofthe first conductive semiconductor layer; a second step of forming ahigh-resistance semiconductor layer on the first conductivesemiconductor layer with a low conductivity material such that the v-pitstructure of the first conductive semiconductor layer is flattened; anda third step of sequentially forming an active layer and a secondconductive semiconductor layer on the flat first conductivesemiconductor layer.

In addition, according to another embodiment of the present invention, amethod for manufacturing nitride semiconductor light-emitting deviceincludes: a first step of growing a first conductive semiconductor layeron a substrate while forming a v-pit structure on an upper surface ofthe first conductive semiconductor layer; a second step of forming ahigh-resistance semiconductor layer on the first conductivesemiconductor layer with a low conductivity material such that the v-pitstructure of the first conductive semiconductor layer is flattened; athird step of forming an active layer on the flat high-resistancesemiconductor layer while forming a v-pit structure on an upper surfaceof the active layer; and a forth step of forming a second conductivesemiconductor layer while flattening the v-pit structure of the activelayer.

Desirably, after forming a first conductive semiconductor layer on thehigh-resistance semiconductor layer flattened at the third step, theactive layer and the second conductive semiconductor layer are formed.

Advantageous Effects

As described above, the light-emitting device of the present inventioncomprises an active layer formed flat using a low conductivity materialon a first conductive semiconductor layer having a v-pit structure onthe upper surface thereof, and a second conductive semiconductor layer,or has a v-pit structure on a junction surface between a secondconductive semiconductor layer and an active layer formed flat using alow conductivity material is formed on a first conductive semiconductorlayer having a v-pit structure on the upper surface thereof. Thus, av-pit area has a thickness equal to or greater than a critical thicknessand thus has very low conductivity, thereby preventing the flow of acurrent, while the remaining area has a thickness equal to or less thana critical thickness and thus a current can flow upwards. Thus, thepresent invention has effects in reducing current leakage and enhancingdurability of other elements while reducing non-radiative recombinationgenerated by threading dislocation, thereby minimizing degradation ofluminosity.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view showing a structure of a nitridesemiconductor light-emitting device according to a first embodiment ofthe present invention.

FIG. 2 is a flow diagram briefly showing a method for manufacturing anitride light-emitting device according to the first embodiment of thepresent invention.

FIGS. 3a and 3b are a plan view and a perspective view illustrating SEMimages showing v-pit structures on an n-type GaN layer acquired fromcontrol of growth conditions according to the first embodiment.

FIGS. 4a and 4b are graphs showing light-emitting characteristicsaccording to a wavelength of a light-emitting device according to thefirst embodiment of the present invention in comparison with aconventional technique.

FIG. 5 is a cross sectional view showing a structure of a nitridelight-emitting device according to a second embodiment of the presentinvention.

FIG. 6 is a flow diagram briefly showing a method for manufacturing anitride light-emitting device according to the second embodiment of thepresent invention.

FIGS. 7a and 7b are a plan view and a perspective view illustrating SEMimages showing v-pit structures on an n-type GaN layer acquired fromcontrol of growth conditions according to the second embodiment.

FIG. 8 is cross sectional TEM images showing V-pit structure formed onactive layer.

FIGS. 9a and 9b are graphs showing light-emitting characteristicsaccording to a wavelength of a light-emitting device according to thesecond embodiment of the present invention in comparison with aconventional technique.

BEST MODE

In the following description, the structural or functional descriptionspecified to exemplary embodiments according to the concept of thepresent invention is intended to describe the exemplary embodiments, soit should be understood that the present invention may be variouslyembodied, without being limited to the exemplary embodiments. While thepresent invention will be described in conjunction with exemplaryembodiments thereof, it is to be understood that the present descriptionis not intended to limit the present invention to those exemplaryembodiments. On the contrary, the present invention is intended to covernot only the exemplary embodiments, but also various alternatives,modifications, equivalents and other embodiments that may be includedwithin the spirit and scope of the present invention.

Further, relative terms, such as “lower” or “bottom” and “upper” or“top” may be used herein to describe relationship of one element toother elements as illustrated in the Figures. It will be understood thatrelative terms are intended to encompass different orientations of thedevice in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on the “upper” side of the other elements.

The exemplary term “lower” can, therefore, encompass both an orientationof “lower” and “upper”, depending upon the particular orientation of thefigure. Similarly, if the device in one of the figures were turned over,elements described as “below” or “beneath” other elements would then beoriented “above” the other elements. The exemplary terms “below” or“beneath” can, therefore, encompass the orientations of both above andbelow.

Also, for convenience of understanding of the elements, in the figures,sizes or thicknesses may be exaggerated to be large (or thick), may beexpressed to be small (or thin) or may be simplified for clarity ofillustration, but due to this, the protective scope of the presentinvention should not be interpreted narrowly.

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

First Embodiment

FIG. 1 is a cross sectional view showing a structure of a light-emittingdevice according to the present invention. A light-emitting devicecomprises a substrate 110; a first conductive semiconductor layer 120140 formed on the substrate 110; a high-resistance semiconductor layer130 formed on the first conductive semiconductor layer 120 140; anactive layer 150 formed on the high-resistance semiconductor layer 130;and a second conductive semiconductor layer 160 formed on the activelayer 150, wherein the light-emitting device has a V-shaped (v-pit)structure v at a junction surface between the high-resistancesemiconductor layer 130 and the first conductive semiconductor layer 120and has a plane or a gradual curved plane structure at a junctionsurface between the high-resistance semiconductor layer 130 and theactive layer 150.

The substrate 110 was provided as a base layer for arranginglight-emitting device, the substrate 110 may be formed by using atransparent material including sapphire substrate, also the substrate110 may be formed by using a material such as GaN-based substrate, SiC,Si, ZnO, or the like in place of the sapphire.

The first conductive semiconductor layer 120 formed on the substrate 110may be consisted of an n-type semiconductor layer providing electrons tothe active layer 150, and may include n-type semiconductor layer whereinn-type impurities are doped with a material such as Si, Ge, Sn, etc. Forinstance, the first conductive semiconductor layer 120 may be formed byusing a material such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN,etc.

A buffer layer (not shown) may be added between the substrate 110 andthe first conductive semiconductor layer 120 to improve lattice matchingaccording to a type of the substrate and a growth process of thesubstrate.

A partial top surface of the first conductive semiconductor layer 120 isexposed and an electrode 121 is formed thereto.

A transparent electrode 170 made of a material such as ITO is formed onthe second conductive semiconductor layer 160 and a bonding electrode isformed on the transparent electrode 170.

The second conductive semiconductor layer 160 formed on the active layer150 may be consisted of a p-type semiconductor layer injecting holes tothe active layer 150, and may include a p-type semiconductor layerwherein p-type impurities are doped with a material such as Mg, Zn, Ca,Sr, Ba, etc. For instance, the second conductive semiconductor layer 160may be formed of by using a material such as GaN, AlN, AlGaN, InGaN,InN, InAlGaN, AlInN, etc.

The active layer 150 is interposed between the first conductivesemiconductor layer 120 and the second conductive semiconductor layer160, electrons and holes recombine therein, and a transition to a lowerenergy level occurs. As a result, the active layer 150 generates lighthaving a corresponding wavelength.

The active layer 150 may be provided as a single-or multi-quantum-wellstructure made of nitride semiconductor containing indium and gallium.

In this embodiment, the first conductive semiconductor layers 120 and140 are formed in multiple layers, the high-resistance semiconductorlayer 130 is interposed between a lower one 120 of the first conductivesemiconductor layers and an upper one 140 of the first conductivesemiconductor layers. Particularly, the light-emitting device has av-pit structure v at the junction surface between the lower firstconductive semiconductor layer 120 and the high-resistance semiconductorlayer 130, and has a plane or a gradual curved plane structure at ajunction surface between the high-resistance semiconductor layer 130 andthe upper first conductive semiconductor layer 140.

Specifically, the v-pit structure v is formed around a threadingdislocation 101 penetrating a light-emitting device and preventsconcentration of current to the threading dislocation 101.

The v-pit structure v may be formed by controlling lower firstconductive semiconductor layer 120 growth conditions such as a growthtemperature, a growth rate, and an atmospheric gas. After the v-pitstructure v is formed on the lower first conductive semiconductor layer120, the high-resistance semiconductor layer 130 is formed on the lowerfirst conductive semiconductor layer 120 with relatively lowconductivity material such that the v-pit structure v of the lower firstconductive semiconductor layer 120 is flattened.

On the other hand, the junction surface between the high-resistancesemiconductor layer 130 and the upper first conductive semiconductorlayer 140 is a plane structure. At this point, in the present invention,the ‘plane’ structure is not strictly limited to a plane definedmathematically, and it should be understood the plane includes thegradual curved plane structure in a range of not having a V-shaped(v-pit) structure.

The high-resistance semiconductor layer 130 may be provided by an n-typeresultant semiconductor layer or an unintentionally doped semiconductorlayer not arbitrary doped. A thickness of the high-resistancesemiconductor layer 130 is desirably in a range of 10 nm to 1000 nm.

Further, in this embodiment, after the upper first conductivesemiconductor layer 140 is thinly formed on the high-resistancesemiconductor layer 130, the active layer 150 and the second conductivesemiconductor layer 160 are formed thereon.

In this way, a remaining area excluding a v-pit area has a thicknessequal to or less than a critical thickness and thus a current may flowto the second conductive semiconductor layer 160, while the v-pit areahas a thickness equal to or greater than a critical thickness and thushas very low conductivity, thereby preventing the flow of a current.That is, the current generally concentrated through a threadingdislocation is covered with the low conductivity material and isprevented, thus the present invention is capable of reducing currentleakage, enhancing durability of other elements, and reducingnon-radiative recombination generated by the threading dislocation,thereby minimizing degradation of luminosity.

On the other hand, the high-resistance semiconductor layer 130 has lowconductivity and this improves the transverse current spreading, thusoverall uniform light-emitting characteristics of a light-emitting areaand the reverse voltage characteristics can be improved.

On the other hand, this embodiment is given the first conductivesemiconductor layer 120 and 140, which is a multiple layer structure,but also it may be a single layer structure wherein the active layer 150is formed directly on the high-resistance semiconductor layer 130 andthe junction surface between the high-resistance semiconductor layer 130and the active layer 150 is a plane structure.

FIGS. 4a and 4b are graphs showing light-emitting characteristicsaccording to a wavelength of a light-emitting device according to thefirst embodiment of the present invention (dotted line) in comparisonwith a conventional technique (solid line), wherein FIG. 4a shows a PLspectrum, and FIG. 4b shows an EL spectrum of the device.

As illustrated in FIG. 4, the light-emitting device of the presentinvention was improved in comparison with conventional technique in thePL spectrum and the EL spectrum.

Second Embodiment

FIG. 5 is a cross sectional view showing a structure of a light-emittingdevice according to the present invention. A light-emitting devicecomprises: a substrate 210; a first conductive semiconductor layer 220240 formed on the substrate 210; a high-resistance semiconductor layer230 formed on the first conductive semiconductor layer 220 240; anactive layer 250 formed on the high-resistance semiconductor layer 230;and a second conductive semiconductor layer 260 formed on the activelayer 250, wherein the light-emitting device has a V-shaped (v-pit)structure v1, v2 on each of junction surfaces between thehigh-resistance semiconductor layer 230 and the first conductivesemiconductor layer 220 and between the active layer 250 and the secondconductive semiconductor layer 260, and has a flat surface with no v-pitstructure at a junction surface between the high-resistancesemiconductor layer 230 and the active layer 250.

The substrate 210 is provided as a base layer for arranginglight-emitting device, the substrate 210 may be formed by using atransparent material including sapphire substrate, also the substrate210 may be formed by using a material such as a GaN-based substrate,SiC, Si, ZnO, or the like in place of the sapphire.

The first conductive semiconductor layer 220 formed on the substrate 210may consist of an n-type semiconductor layer providing electrons to theactive layer 250, and may include an n-type semiconductor layer whereinn-type impurities are doped with a material such as Si, Ge, Sn, etc. Forinstance, the first conductive semiconductor layer 220 may be formed byusing a material such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN,etc.

A buffer layer (not shown) may be added between the substrate 210 andthe first conductive semiconductor layer 220 to improve lattice matchingaccording to a type of the substrate and a growth process of thesubstrate.

A partial top surface of the first conductive semiconductor layer 220 isexposed and an electrode 221 is formed thereon.

A transparent electrode 270 made of a material such as ITO is formed onthe second conductive semiconductor layer 260 and a bonding electrode isformed on the transparent electrode 270.

The second conductive semiconductor layer 260 formed on the active layer250 may consist of a p-type semiconductor layer injecting holes to theactive layer 250, and may include a p-type semiconductor layer whereinp-type impurities are doped with a material such as Mg, Zn, Ca, Sr, Ba,etc. For instance, the second conductive semiconductor layer 260 may beformed by using a material such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN,AlInN, etc.

The active layer 250 is interposed between the first conductivesemiconductor layer 220 and the second conductive semiconductor layer260, electrons and holes recombine therein, and a transition to a lowerenergy level occurs. As a result, the active layer 250 generates lighthaving a corresponding wavelength.

The active layer 250 may be provided as a single- or multi-quantum-wellstructure made of nitride semiconductor containing indium and gallium.

In this embodiment, the first conductive semiconductor layers 220 and240 are formed in multiple layers, and the high-resistance semiconductorlayer 230 is interposed between a lower one 220 of the first conductivesemiconductor layers and an upper one 240 of the first conductivesemiconductor layers.

Particularly, in this embodiment, the light-emitting device has aV-shaped (v-pit) structure v1, v2 individually at each of junctionsurfaces between the lower first conductive semiconductor layer 220 andthe high-resistance semiconductor layer 230, and between the activelayer 250 and the second conductive semiconductor layer 260.

Desirably, the junction surface between the high-resistancesemiconductor layer 230 and the upper first conductive semiconductorlayer 240 has a plane or a gradual curved plane structure.

Specifically, the v-pit structure v1, v2 is formed around a threadingdislocation 201 penetrating a light-emitting device and preventconcentration of current to the threading dislocation 201.

In this embodiment, a first v-pit structure v1 may be formed bycontrolling lower first conductive semiconductor layer 220 growthconditions such as a growth temperature, a growth rate, and anatmospheric gas. After the v-pit structure v1 is formed on the lowerfirst conductive semiconductor layer 220, the high-resistancesemiconductor layer 230 is formed on the lower first conductivesemiconductor layer 220 with relatively low conductivity material suchthat the v-pit structure v1 of the lower first conductive semiconductorlayer 220 is flattened. A second v-pit structure v2 may be formed on theactive layer 250 according to the same process.

Desirably, a depth of the second v-pit structure v2 may be decided in arange of 100 Å to 1 μm.

On the other hand, the junction surface between the high-resistancesemiconductor layer 230 and the upper first conductive semiconductorlayer 240 is a plane structure. At this point, in the present invention,the ‘plane’ structure is not strictly limited to plane definedmathematically, and it should be understood the plane includes thegradual curved plane structure in a range of not having a V-shaped(v-pit) structure.

The high-resistance semiconductor layer 230 may be provided by an n-typeresultant semiconductor layer or an unintentionally doped semiconductorlayer not arbitrary doped. A thickness of the high-resistancesemiconductor layer 230 is desirably in a range of 10 nm to 1000 nm.

Further, in this embodiment, after the upper first conductivesemiconductor layer is 240 thinly formed on the high-resistancesemiconductor layer 230, the active layer 250 and the second conductivesemiconductor layer 260 are formed thereon.

In this way, a remaining area excluding a v-pit area has a thicknessequal to or less than a critical thickness and thus a current may flowto the second conductive semiconductor layer 260, while the v-pit areahas a thickness equal to or greater than a critical thickness and thushas very low conductivity, thereby preventing the flow of a current.That is, the current generally concentrated through a threadingdislocation is covered with the low conductivity material and isprevented, thus the present invention is capable of reducing currentleakage, enhancing durability of other elements, and reducing anon-radiative recombination generated by the threading dislocation,thereby minimizing degradation of luminosity.

In particular, the second conductive semiconductor layer 260 which isformed when a sloped surface exists caused by the second v-pit structurev2 formed on the active layer 250 has an effect of preventing current asa thin film having a low conductive semi-insulating characteristic formson a portion of V-shaped distortion structure. Also, a carrier is easilyinjected from the second conductive semiconductor layer 260, which is onthe active layer 250, to the V-shaped sloped surface so that it makes aninjection of the carrier up to the lower part of the active layer 250easy, thus, the effective light-emitting layer and the efficiency of theentire device can be increased.

On the other hand, the high-resistance semiconductor layer 230 has lowconductivity and this improves the transverse current spreading, thusoverall uniform light-emitting characteristics on light-emitting areaand the reverse voltage characteristics can be improved.

On the other hand, this embodiment is given the first conductivesemiconductor layer 220 and 240 is multiple layer structure but also itmay be a single layer structure, in this case, the active layer 250 isformed directly on the high-resistance semiconductor layer 230, and ajunction surface between the high-resistance semiconductor layer 230 andthe active layer 250 is a plane structure.

On the other hand, as shown in FIG. 5, the second conductivesemiconductor layer 270 may be a flat surface, but may have a v-pitstructure on the surface thereof.

FIGS. 9a and 9b are graphs showing light-emitting characteristicsaccording to a wavelength of a light-emitting device according to thesecond embodiment of the present invention (dotted line) in comparisonwith the conventional technique (solid line), wherein FIG. 9a shows a PLspectrum, and FIG. 9b shows an EL spectrum of the device.

As illustrated in FIG. 9, the light-emitting device of the presentinvention was improved in comparison with conventional technique in thePL spectrum and the EL spectrum.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

DESCRIPTION OF THE REFERENCE NUMERALS IN THE DRAWINGS

101, 201: threading dislocation, 110, 210: substrate

120, 220: lower first conductive semiconductor layer, 121, 221:electrode

130, 230: high-resistance semiconductor layer

140, 240: upper first conductive semiconductor layer

150, 250: active layer, 160, 260: second conductive semiconductor layer

170, 270: transparent electrode 171, 271: bonding electrode

v, v1, v2: v-pit structure

1. A nitride semiconductor light-emitting device, comprising: asubstrate; a first conductive semiconductor layer formed on thesubstrate; a high-resistance semiconductor layer formed on the firstconductive semiconductor layer; an active layer formed on thehigh-resistance semiconductor layer; and a second conductivesemiconductor layer formed on the active layer, wherein the nitridesemiconductor light-emitting device has a V-shaped (v-pit) structure ata junction surface between the high-resistance semiconductor layer andthe first conductive semiconductor layer, and has a plane or a gradualcurved plane structure at a junction surface between the high-resistancesemiconductor layer and the active layer.
 2. The nitride semiconductorlight-emitting device of claim 1, wherein the junction surface betweenthe high-resistance semiconductor layer and the active layer is a flatsurface with no v-pit structure.
 3. The nitride semiconductorlight-emitting device of claim 1, wherein the active layer has a planestructure at a junction surface between the active layer and the secondconductive semiconductor layer.
 4. A nitride semiconductorlight-emitting device, comprising: a substrate; a first conductivesemiconductor layer formed on the substrate; a high-resistancesemiconductor layer formed on the first conductive semiconductor layer;an active layer formed on the high-resistance semiconductor layer; and asecond conductive semiconductor layer formed on the active layer,wherein the nitride semiconductor light-emitting device has a V-shaped(v-pit) structure at each of junction surfaces between thehigh-resistance semiconductor layer and the first conductivesemiconductor layer and between the active layer and the secondconductive semiconductor layer, and has a flat surface with no v-pitstructure at a junction surface between the high-resistancesemiconductor layer and the active layer.
 5. The nitride semiconductorlight-emitting device of claim 4, wherein the junction surface betweenthe high-resistance semiconductor layer and the active layer has a planeor a gradual curved plane structure.
 6. The nitride semiconductorlight-emitting device of claim 4, wherein the second conductivesemiconductor layer has a v-pit structure.
 7. The nitride semiconductorlight-emitting device of claim 1, wherein the high-resistancesemiconductor layer has a silicon impurity concentration of 10¹⁸/cm³ orless.
 8. The nitride semiconductor light-emitting device of claim 1,wherein the high-resistance semiconductor layer has a magnesium impurityconcentration equal to or greater than 10¹⁶/cm³.
 9. The nitridesemiconductor light-emitting device of claim 1, wherein thehigh-resistance semiconductor layer has a thickness of 10 nm to 1000 nm.10. A method for manufacturing a nitride semiconductor light-emittingdevice, the method comprising: a first step of growing a firstconductive semiconductor layer on a substrate while forming a v-pitstructure on an upper surface of the first conductive semiconductorlayer; a second step of forming a high-resistance semiconductor layer onthe first conductive semiconductor layer with a low conductivitymaterial such that the v-pit structure of the first conductivesemiconductor layer is flattened; and a third step of sequentiallyforming an active layer and a second conductive semiconductor layer onthe flat high-resistance semiconductor layer.
 11. A method formanufacturing nitride semiconductor light-emitting device, the methodcomprising: a first step of growing a first conductive semiconductorlayer on a substrate while forming a v-pit structure on an upper surfaceof the first conductive semiconductor layer; a second step of forming ahigh-resistance semiconductor layer on the first conductivesemiconductor layer with a low conductivity material such that the v-pitstructure of the first conductive semiconductor layer is flattened; athird step of forming an active layer on the flat high-resistancesemiconductor layer while forming a v-pit structure on an upper surfaceof the active layer; and a forth step of forming a second conductivesemiconductor layer while flattening the v-pit structure of the activelayer.
 12. The method for manufacturing nitride semiconductorlight-emitting device of claim 10, wherein after forming a firstconductive semiconductor layer on the high-resistance semiconductorlayer flattened at the third step, the active layer and the secondconductive semiconductor layer are formed.
 13. The method formanufacturing nitride semiconductor light-emitting device of claim 10,wherein the high-resistance semiconductor layer has a thickness of 10 nmto 1000 nm.
 14. The nitride semiconductor light-emitting device of claim4, wherein the high-resistance semiconductor layer has a siliconimpurity concentration of 10¹⁸/cm³ or less.
 15. The nitridesemiconductor light-emitting device of claim 4, wherein thehigh-resistance semiconductor layer has a magnesium impurityconcentration equal to or greater than 10¹⁶/cm³.
 16. The nitridesemiconductor light-emitting device of claim 4, wherein thehigh-resistance semiconductor layer has a thickness of 10 nm to 1000 nm.17. The method for manufacturing nitride semiconductor light-emittingdevice of claim 11, wherein after forming a first conductivesemiconductor layer on the high-resistance semiconductor layer flattenedat the third step, the active layer and the second conductivesemiconductor layer are formed.
 18. The method for manufacturing nitridesemiconductor light-emitting device of claim 11, wherein thehigh-resistance semiconductor layer has a thickness of 10 nm to 1000 nm.